The last ten years have seen an important increase in the volume of dredging activity, of which an increasing proportion is performed on solid rock. This situation is explained by the increased depth required by marine infrastructure projects and by the geological characteristics of certain regions such as the Persian Gulf. All projections indicate that this tendency of growth will continue in the next decade.
In response to this evolution, dredgers with increasingly powerful cutter heads are operating in construction areas; allowing a higher production rate at a lower cost compared to the traditional drilling and blasting method.
The optimal exploitation of a dredge implies a good geological knowledge of the site. In particular, the position of the rock zones most resistant to cutting must be known because they should be attacked prudently to avoid undue wear and damage to the cutter.
However, in reality, the quality and depth of the rock frequently varies abruptly both in the vertical and horizontal directions. Thus, the cutter head 4 (FIG. 1), can encounter a few meters of loose ground (e.g. sand) 2 followed by a rock 3 more resistant than concrete. In most cases, a document of invitation to tender will give an indication on the geological and geotechnical situ characteristics but it is often insufficient and incomplete. The area of dredging sites is typically a few square kilometers and the distance between exploratory boreholes is typically several hundred meters, whereas shallow rock zones often measure about ten meters only. Such hard spots frequently remain undetected until hit by the cutter head. The simple drilling of additional random boreholes, does not improve the situation.
Traditionally, the dredge master is faced with two possible options:                trying to use “brute force” to maximize the production output, with a high risk of rupture and thus of frequent stops for unplanned repair;        avoiding damage to the cutter suction dredge by limiting the cutting power, which involves an unnecessarily low production output in the non-rock zones.        
The present invention aims to overcome the problems in the art by providing a system that receives high resolution seismic velocity information on the material in advance of the cutter head, and can provide specific adjustment to the cutting parameters in response there to, optionally in addition to the low resolution information usually already available.
The high resolution information is acquired and updated while dredging. The seismic data can be used to fine tune an existing geological model close by the cutter head, during the dredging process itself via seismic velocity measurements close around and in front of the cutter head.